• 한국식품과학회지
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• 제53권6호
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• pp.815-818
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• 2021

The objective of this study was to develop a differential medium with improved selectivity for the isolation of Bacillus cereus. Mannitol egg yolk polymyxin medium supplemented with D-galactose allowed the differentiation of diarrheal- and emetic-type B. cereus through pH monitoring. The pH of the medium decreased significantly when incubating the emetic-type B. cereus, whereas the pH change was not significant when incubating the diarrheal-type. The addition of pH indicators, such as methyl red and phenol red, to the medium allowed visual differentiation between diarrheal- and emetic-type B. cereus. A solid agar medium was also developed by optimizing the concentrations of medium components such as monosaccharides, agar, egg yolk enrichment, pH indicators, and antibiotics. This study indicates the possibility of applying selective media for the differentiation of diarrheal- and emetic-type B. cereus.

• 미생물학회지
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• 제45권2호
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• pp.208-214
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• 2009

장류에서 식중독 미생물인 Bacillus cereus의 계수 방법상 문제점을 해결하기 위하여, B. cereus 선택 배지인 mannitol-egg york-polymyxin B (MYP)에서 자란 약 1,500개의 집락들을 형태적 차이에 따라 12종으로 분류하였다. 생화학 특성 및 16S rRNA 유전자의 염기서열 분석 결과 집락 주위로 환을 형성하는 직경 11~16 mm 크기의 집락들은 B. cereus 와 B. cereus subsp. cytotoxis로 동정되었고, 환을 형성하지 않아 B. cereus 계수에 포함시키지 않았던 직경 5 mm 크기의 분홍색 집락은 B. cereus로, 6.5 mm 크기의 이중환을 형성하여 B. cereus로 계수하기가 모호하였던 붉은색 집락은 B. cereus로 동정되었다. 나머지 세 종들은 Enterococcus sp., Brevibacillus sp., B. subtilis로 밝혀졌다. B. cereus로 동정된 9종 모두에서 적어도 한 종류 이상의 B. cereus 독소 유전자들을 함유하고 있었지만 다른 형태들에서는 발견되지 않았다.

• 한국식품과학회지
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• 제52권6호
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• pp.678-684
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• 2020

The objective of this study was to identify the fermentation characteristics of Bacillus thuringiensis and emetic, non-emetic Bacillus cereus using analytical profile index (API) test. Ten strains of B. thuringiensis and 10 strains of B. cereus including 3 strains of emetic type were used at the same concentrations. The differences of fermentation characteristics between the B. thuringiensis and B. cereus was not obvious, but the differences between the non-emetic and emetic B. cereus were distinctive. Seven among 50 substrates were negative for all non-emetic B. cereus strains and positive for all emetic strains, and three substrates among additional 12 substrates had the same tendency. From these differences, 3 emetic B. cereus strains were not indicated as B. cereus by API test. These results indicate that API test is not a suitable method to identify some strains of emetic B. cereus, and the distinctive differences in substrate utilization can be used to improve selective media.

• 한국식품위생안전성학회지
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• 제22권4호
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• pp.388-394
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• 2007

본 연구는 현행 식품공전상 제시되어 있는 식중독균 분리배지의 평가를 위해 Salmonella spp., Bacillus cereus, Listeria monocytogenes, Vibrio parahaemolyticus, Staphylococcus aureus의 5가지 식중독세균용 29가지 분리 선택배지를 Broth와 Food에서 시험하였다. Food는 닭고기, 쌀, 돼지고기, 고등어를 대상으로 5가지 식중독균을 접종후 균주의 recovery를 확인하였고. Broth는 5가지 식중독세균용 29가지 분리 선택배지를 사용하였다. Broth에서는 각 세정균에 대한 분리배지들 간에 유의적인 차이가 없었으나(P<0.05), Food에서는 그 차가 크지는 않았으나, 분리선택배지간의 분리능에 통계적 유의차가 존재하였다. 식품공전에 등재된 전통적인 분리 선택배지에서 분리된 균수가 Chromogenic 배지 등 새로운 선택배지에서 분리된 균수보다 많았다. 국제적으로 등재된 배지간의 선택성의 차이가 존재하였으며, 추후 다양한 배지가 식품공전에 등재되기 위해서는 추가 연구가 필요하다.

• 한국식품과학회지
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• 제35권1호
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• pp.97-102
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• 2003

Cook-chill 제품의 원료로 사용하는 시금치와 수세한 시금치에 대해 Aeromonas hydrophila, Escherichia coli O157:H7, Plesiomonas shigelloides, Pseudomonas aeruginosa, Salmonella spp., Shigella spp., Yersinia enterocolitica, Bacillus cereus, Campylococcus spp., Clostridium perfringens, Listeria monocytogenes, Staphylococcus aureus 등 12종류의 병원성세균의 존재 여부를 확인하였다. 이들 시금치로부터 4종의 병원성세균을 분리하여 API kit와 ATB 자동 동정기를 포함한 형태학적 및 생화학적 방법에 의해 동정하였다. MacConkey agar에서 분리된 균은 그람 음성 간균으로 glucose를 이용하여 gas를 생성하며, lactose 음성, sucrose 양성, lysine 양성으로 ATP system에서 A. hydrophila 종에 대해 99.9%의 상동성을 보였다. Cereus Selective agar에서 분리된 균은 그람 양성 간균, 포자 형성균으로 catalase 양성, mannitol 음성, lecithinase 양성, Simmon's citrate 음성, $NO_2$ 생성 양성, arginine 양성균으로 ATB system에서 B. cereus 종에 대해 99.8%의 상동성을 보였다. Clostridium Perfringens agar에서 분리된 균은 그람 양성 간균, 혐기성균으로 포자를 형성하며, mannitol 양성, lecithinase 양성으로 ATB system에서 C. perfringens 종에 대해 99.9%의 상동성을 보였다. Baird-Parker agar에서 분리된 균주는 그람 양성 구균으로 mannitol, lecithinase, lactose, clumping factor, coagulase 및 hemolysin 양성, xylose 음성으로 ATB system에서 S. aureus 종에 대해 97.8%의 상동성을 보였다. Salmonella spp., E. coli O157:H7, Y. enterocolitica를 포함한 다른 병원성세균은 분리되지 않았다. 시금치에서 분리한 S. aureus 5균주 중 2균주는 SET-RPLA kit에서 enterotoxin type A를 생성하였고 3균주는 enterotoxin을 생성하지 않았다. B. cereus 5균주는 CRET-RPLA kit에서 모두 enterotoxin을 생성하였다.

• 한국환경보건학회지
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• 제41권6호
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• pp.397-404
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• 2015

Objectives: The aim of this study is to investigate microbial contamination in the school food service environment for the assessment of microbial food safety. Methods: We collected both swab samples from tables and desks and airborne bacterial samples from an elementary school (School A) and a high school (School B). Heterotrophic plate count, total coliform, Staphylococcus aureus, and Bacillus cereus were measured with selective media to quantify microbial concentration. PCR assay targeting 16S rRNA genes was performed to identify the strains of S. aureus and B. cereus isolated. In addition, we made a food service checklist for the locations to evaluate the food service environment. A Wilcoxon test was employed to examine the differences in microbial concentration between before lunchtime and afterwards. Results: Heterotrophic plate counts showed higher levels after-lunch compared to before-lunch at School B. However, levels of S. aureus were higher in the after-lunch period (p<0.05) in both classrooms and in the cafeteria in School A. B. cereus was only sparsely detected in School B. Several samples from food dining carts were found to be contaminated with bacteria, and facilities associated with food delivery were found to be vulnerable to bacterial contamination. Although microbial concentrations in the air showed little difference between before- and after-lunchtime in the cafeteria in School A, those in classrooms were greater after-lunchtime at both schools. Conclusion: Our results suggested that the microbial safety in schools after lunchtime of concern. Necessary preventive measures such as hygiene education for students and food handlers should be required to minimize microbial contamination during food service processes in schools.

• 한국환경보건학회지
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• 제37권5호
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• pp.376-386
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• 2011

Objectives: The aim of this study was to evaluate the microbial hazards posed by food utensils and fixtures in food service operations at selected middle and high schools located in Seoul, Korea. Methods: We collected 200 samples of utensils and fixtures including cups, spoons/chopsticks, food trays and tables from five different schools in Seoul. Target microorganisms of this study were divided into two groups: total bacterial count and total coliform as indicators of microbial contamination and Bacillus cereus and Staphylococcus aureus as pathogens of food poisoning. We used selective media to quantify microbial concentration and 16S rRNA PCR assay for qualitative analysis. In addition, intensive interviews with nutritionists were conducted and observations were made to identify factors that may affect microbial contamination. Logistic regression analysis was employed to examine the relationship between the microbial concentration and operation characteristics of each operation. Results: The level of microbial concentration in school B and C were significantly lower than in school A, D and E (p<0.05). Some samples from school A, D and E showed over 3.4 log CFU/100 $cm^2$ (total bacterial count) and 1.0 log CFU/100 $cm^2$ (total coliform), which requires immediate hygienic action. The number of customers per staff member, periodicity of hygiene education for staff and daily operation time of sterilizers were also found to be important factors related with the microbial contamination of food service operations. Conclusions: These results suggested that not only a HACCP (Hazard Analysis and Critical Control Point) approach, but also efforts to assess internal risk factors within operations be needed to reduce the microbial contamination of food utensils and fixtures. This study is expected to provide preliminary data for assessing microbial hazards in food service operations.